Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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437 views

Dielectric slab counter-intuitive formula?

For the calculation of force on one of the two equal(in magnitude, opposite in sign) point charges separated by $r$ with a dielectric slab of dielectric constant $K$ and width $d$ in between, the ...
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1answer
110 views

Green function solutions in electrostatics

I have a conducting plate on $x$-$y$ plane. So I have a boundary condition at $z=0$ $\Phi=0$ but, for $z>0$ I have a point charge at z=a which is expected to create a potential. $$ ...
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2answers
88 views

Two capacitor plates with equal positive charges $q$

I read in a book that if both the plates of a parallel plate capacitor are given equal positive charges $q$, then the charges on the facing surfaces will be zero and the charge on the outer surfaces ...
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1answer
86 views

Electric force between charges in two different media

As far as I know, Coulomb's law of electrostatic force is applicable on two different charges situated in same medium. But if two individual charges are in different media (say one charge on a iron ...
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1answer
64 views

How can electric field representation be obtained from Enge representation using Maxwell's equations?

Suppose we have a long electric capacitor. Let $L$ be its length ($z$ coordinate), $W$ its width ($y$ coordinate), and $D$ its full height (full aperture; $x$ coordinate). Let $L\gg W\gg D$. The ...
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15 views

potential inside a cylindrical shell in terms of the surface potential?

Given a potential distribution $V(\phi)$ at the surface of an infinite cylindrical shell, is there an easy way to derive the potential inside the cylinder. No charges or currents anywhere.
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Electricity. I'm finding difficulty answering this question [on hold]

Consider 3 identcal spheres, A,B,C. A carries a +5q charge. B carries a -q charge. C carries no net charge. Spheres A and B are touches together and then seperated. Sphere C is then touched to Sphere ...
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9answers
3k views

Why can't electrostatic field lines form closed loops?

My physics textbook says "Electrostatic field lines do not form closed loops. This is a consequence of the conservative nature of electric field." But I can't quite understand this. Can anyone ...
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2answers
40 views

Paradox in electrostatics in relation to Gaussian surfaces?

I have encountered something that is very confusing. My problem is this. I am assuming two infinite cubical Gaussian surfaces sharing a common side. One of the cubes contains a charge $q_1$ at a ...
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5answers
12k views

Electric potential vs potential difference

What is the difference between electric potential and potential difference? In our course book, they are given as separate topics but their definition is given the same.
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1answer
13 views

How to calculate surface density of conducting plates, given zero potential condition and another conducting plate [on hold]

Suppose there are three conducting plates at $z=6,3,0$(m) surface. The surface at $z=3$ has static surface-charge of $2C/m^2$, and the surfaces at $z=6$ and $z=0$ have zero electrostatic potential. ...
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2answers
19 views

How can I use volume charge density to find charge density constant knowing charge Q

I have an insulating sphere of radius R that has a total charge Q. It is distributed as $\rho$= $\rho_0*r^4$. I know that the charge is equal to Q and I'm trying to solve for $\rho_0$. I've tried to ...
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0answers
7 views

What charge will accumulate on an aluminium rod when rubbed with amber? [on hold]

An aluminium rod is held with an insulating handle.Then the rod is rubbed with amber.What will happen to the rod and why?(with reference to triboelectric series)
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1answer
24 views

Electromagnetism and static electricity

What is the difference between electromagnetism and static electricity? Also electromagnetic waves are mediated by photons , what mediates static electricity?
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1answer
130 views

Static electricty and fields inside of the conductor?

I have a few related questions about static electricity and conductors. 1. when we say static electric field inside a conductor is zero, let us take an example of two concentric conductors, outer one ...
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0answers
46 views

Potential due to infinite plate carrying a finite charge

I've solved many problems where something is grounded and you've to figure out the charge distribution. The general strategy is to set the potential of the grounded thing equal to zero and solve. ...
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2answers
2k views

Electrostatic Pressure Concept

There was a Question bothering me. I tried solving it But couldn't So I finally went up to my teacher asked him for help . He told me that there was a formula for Electrostatic pressure ...
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3answers
116 views

Is the charge distribution for an electric field unique?

If the electric field and boundary conditions are known exactly for a region of space, is it true that there exists only one charge distribution in that region of space that could have produced it? ...
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0answers
42 views

What are some open problems in classical electrodynamics? [duplicate]

I am about to finish reading 'Introduction to Electrodynamics' by David Griffiths. Throughout the textbook, Griffiths makes frequent references to current literature (mostly articles from American ...
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0answers
26 views

How can a potential step be modelled?

a potential step is given by function $V(x) = V_o, x\geq 0$ and $V(x) = 0, x\leq 0$ Using the relation $- \frac{dV}{dx} = \vec E$ I take the negative derivative of this function, i'll get ...
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1answer
78 views

Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
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0answers
16 views

Defining the region in Laplace's equation

1) Consider a sphere S centered at the origin O, where a charge q is present. Is Laplace's equation applicable in the region S? No, right? 2)This is where I go crazy.... Instead of considering the ...
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2answers
71 views

What is the potential field of an ion near the Bohr radius?

I figure that at large enough distances, the potential field of an ion is just the Coulomb potential for its net charge. But what happens at scales comparable to the ion's Bohr radius? Could there be, ...
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1answer
335 views

How can one explain the Kelvin Water drop experiment without assuming the container to already possess a positive charge?

Kelvin Water Dropper experiment refers to the electrostatic generator invented by Lord Kelvin, which uses falling water to generate a voltage by electrostatic induction occurring between ...
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1answer
29 views

What's the Relation between Potential of mechanics and electricity?

As we know that for a conservative force field, there is associated a Potential with the force. But we know there is a potential in electricity (That's voltage). My question is that is there any ...
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1answer
52 views

Electric field and charge density outside two coaxial cylinders

I am working on a problem of electrostatics, and I am having troubles in trying to figure out one part of it. It consists of an inner solid cylinder of radius $a$ with a voltage $V_A$, and an outer ...
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1answer
24 views

Accelerating an electron to a high speed

Suppose there are two vertical metal plates. They are separated apart by a small distance. While one is grounded, the other one has a potential of some $V$. Now suppose electrons are produced at the ...
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0answers
109 views

Resistance of a cylinder contacted by two smaller circular faces

Suppose we have a solid homogeneous cylinder with radius $a$, heigth $h$ and conductivity $\sigma$. The top and the bottom face is contacted with a smaller circular face with radius $b$. How can I ...
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2answers
99 views

Proof that the electric field is conservative

I was told a proof that the electric field was conservative (without using $\nabla$) which used a point charge and showed the following: $$w.d.=\int_c{\vec F \cdot \mathrm{d} \vec l}=\int_c{\vec ...
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1answer
28 views

Electric field on a rod [closed]

We are given a stick of length $L$ with uniformly distributed charge $Q$. One end is at $x = -L$ and the other at origin. A point charge is placed at $x = L$ we have to find a point inside the ...
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20 views

Anyone know of a flow chart or list of common/useful consequences of Maxwell's equations?

I just recently started to appreciate the Maxwell equations. I had never really take the time to study them but I feel like I'm finally more familiar with them. I've noticed that it seems like a lot ...
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1answer
39 views

Electric Flux - What is the point?

Electric flux is a defined quantity that is proportional to the no. of field lines passing through a given area element for a given electric field. It is not proportional to the relative density of ...
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0answers
19 views

Work done by electric field at large to small distances [closed]

Question: How much work is done by the electric field bringing a particle with charge +q from $(x, y) = (0,\infty)$ to point P (origin) by sliding it down the +y-axis? There is a dipole on the x-axis ...
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15 views

how can find the electrostatic force when the two identical charge are placed in different medium [closed]

Charge are placed in different medium and their distance between them is $r$. The identical charges are $q$. Then, what is the formula to find out the force between them?
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21 views

Why are trampolines more likely to give you a static shock when it is sunny?

It could just be in my head but I have noticed that I am more likely to get a static shock from my tramp when it is sunny than when it is not sunny. Is there a reason for this?
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1answer
85 views

Is it equivalent to derive Gauss's law from discrete and continuous source distributions?

I've seen two derivations for Gauss's law in electrostatics. The first assumes a discrete charge distribution, the second a continuous one: Use superposition $$\vec{E}=\sum_{i=1}^n\vec{E}_i,$$ so ...
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1answer
14 views

Plastic and Iron - static and magnetic

I'm wondering if when you have a ball that is made out of plastic but has an inner core of metal. Would that ball if given friction produce static? Or would the static from the outerside of the ...
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0answers
21 views

Gauss's Law - Field with constant direction [closed]

Doing some exercises in the topic of Gauss's Law, I found this problem which I can't seem to understand: Suppose that an electric field in some region is found to have a constant direction but to ...
3
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1answer
79 views

Earnshaw Theorem for ionic solids

Is a single molecule of sodium chloride (say) or a cluster of molecules of NaCl unstable, although macroscopically NaCl is in fact, stable? How can I reason this based on Earnshaw's theorem?
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1answer
44 views

Wait… why exactly does farady's ice pail experiment prove Gauss's law?

You'll notice there are no equations in this: that's because this is a question of morale, not of math. But a humble one at that! I come to learn, not to expound. But don't let that limit the form ...
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2answers
591 views

How can I split a resultant force into its $x$ and $y$ components?

Point charge 3.5μC is located at x = 0, y = 0.30 m, point charge -3.5μC is located at x = 0 y = -0.30 m. What are (a)the magnitude and (b)direction of the total electric force that these charges ...
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2answers
75 views

Electrostatics and two electric charges

How can two identical metallic objects have the same but opposite charges (one loses electrons and one gains electrons) when we know that metals have the ability to lose electrons only?
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1answer
112 views

Charge distribution on a doughnut shaped conductor

In a spherical solid conductor the charge is always on the outer surface.Even if the sphere has a cavity,the surface of the inner cavity can not carry a charge due to Gauss's Law. What would be the ...
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0answers
38 views

Electric Flux through cube from point charge

"A point charge is located at the origin. Calculate the flux of E through a cube centered on the origin and aligned with the Cartesian axes. Evaluate the surface integral directly and verify that the ...
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3answers
117 views

Polarization vector of dielectric electrostatics

I know two laws for Polarization vector of a dielectric material $$\vec P = N q \vec{\Delta L}$$ Where N is the number of dipoles per meter cube, $\vec{\Delta L}$ is the vector that represents the ...
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2answers
307 views

Effect of charges near a parallel plate capacitor

If I charge a parallel plate capacitor and I insert a charged body near one of the plates will there be any interactions like attraction or repulsion? What if I disconnect the battery?
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6answers
485 views

What keeps electrons on a negatively-charged conductor from leaving?

Imagine a negatively charged conductor in a vacuum. The excess electrons will be spread out over the surface such that the net electric field inside the conductor is zero. What keeps these extra ...
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2answers
133 views

Numerically solving 2D poisson equation by FFT, proper units

The 2D Poisson equation is: (1)$$\frac{d^2\varphi(x,y)}{dx^2}+\frac{d^2\varphi(x,y)}{dy^2}=-\frac{\varrho(x,y)}{\epsilon_0\epsilon}$$ And in $k$-space it is in form of: (2)$$(k_x^2+k_y^2) ...
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Why does excess of charge in an isolated conductor move to the surface?

A remark in my textbook goes as follows: "If an excess charge is placed on an isolated conductor, that amount of charge will move entirely to the surface of the conductor. None of the excess charge ...